Adhesives and glues are liquid substances that hold materials together and prevent separation after drying. They often reinforce or provide an alternative to mechanical fasteners. Load-bearing structural adhesives are the only adhesive able to create load-bearing bonds. Construction adhesives form permanent bonds in building materials but are not intended for load-bearing applications. Spray adhesives are useful in applications that bond larger surface areas. Contact adhesives must be placed on both surfaces before joining to properly bond. Instant adhesives, also known as superglues, bond and cure the fastest among all adhesives. Hot melt adhesives join and seal light- to medium-weight materials using hot-melt glue sticks. Wood glues bond wooden parts together, or other materials specifically to wood.